A passive optical network (PON) is one system for providing network access over “the last mile,” which is the final portion of a telecommunications network that delivers communication to customers. A PON is a point-to-multipoint (P2MP) network comprised of an optical line terminal (OLT) at a central office (CO), an optical distribution network (ODN), and optical network units (ONUs) at the user premises. PONs may also comprise remote nodes (RNs) located between the OLTs and the ONUs, for instance at the end of a road where multiple customers reside.
In recent years, time-division multiplexing (TDM) PONs such as gigabit-capable PONs (GPONs) and Ethernet PONs (EPONs) have been deployed worldwide for multimedia applications. In TDM PONs, the total capacity may be shared among multiple users using a time-division multiple access (TDMA) scheme, so the average bandwidth for each user may be limited to below 100 megabits per second (Mb/s).
Wavelength-division multiplexing (WDM) PONs are considered a very promising solution for future broadband access services. WDM PONs can provide high-speed links with dedicated bandwidth up to 10 gigabits per second (Gb/s). By employing a wavelength-division multiple access (WDMA) scheme, each ONU in a WDM PON is served by a dedicated wavelength channel to communicate with the CO or the OLT. Next-generation PONs (NG-PONs) and NG-PON2s may include point-to-point (P2P) WDM PONs (P2P-WDM PONs), which may provide data rates higher than 10 Gb/s. NG-PONs and NG-PON2s may also include time- and wavelength-division multiplexing (TWDM) PONs, which may also provide data rates higher than 10 Gb/s.